Light's criteria

Light's criteria are a set of tests used by doctors to determine if a buildup of fluid in the lung lining (pleural effusion) is caused by heart failure or other medical conditions. The criteria compare fluid and blood values, looking at the amount of protein and a substance called LDH in the fluid versus the blood. If certain thresholds are met—such as higher protein or LDH levels in the fluid—it suggests the fluid is an exudate, often due to infections or inflammation. If not, it's likely a transudate, often caused by conditions like heart failure.